Refrigerating machine



- 2 SheetS-Shee, l

E. KGI

REFRIGERATING MACHINE Filed Aug. 24, 1929 Sept. 20, 1932.

sept. 2o, 1932. E KG, 1,878,403I

REFRIGERAT ING MACHINE Filed Aug. 24. 1929 2 Sheets-Shee- 2 INJENTDFQ M -Eo/ Patented Sept. 20, 1932 UNITED STATES PATENT OFFICE EMIL KGI, 0F WINTERTHUR, SWITZERLAND, ASSIGNOR TO THE FIRM OF- SULZER FRERES SOCIETE ANONYME, F WINTERTHUR, SWITZERLAND REFRIGERATING MACHINE application mea August 24, 1929, serial No. 388,132, and in switzerland october 1s, 192s.

This invention relates to refrigerating mai chines more particularly of the kind in which the refrigerating medium is returned from the evaporator to the condenser by means of a rotary compressor.

Oil is used in the rotary compressor not only to lubricate the moving parts but also to seal the clearances between -such moving parts, and thus to prevent the escape of the refrigerating medium and the consequent ineiiiciency of the machine. Comparatively large quantities of oil are therefore circulated and, as some of the oil gets into the high pressure chamber ofthe compressor, the compressed rerigerating medium or gas 1s passed through an oil separator before reaching the condenser. It is diliicult however to effect perfect separation of the oil owing partly to the nature of some of the refrigerating media used and partly to the fact that the oil is to some extent'atomized in the slot-like clearances of the compressor. Further, in the case of machines which, owing to the nature of the refrigerating medium, have to work with a high degree of superheat, as is ythe case in ammonia machines, the resulting high temperatures cause a partial evaporation of the oil. This evaporated oil can be condensed by cooling but an oil mist is likely to be formed which it is difficult to eliminate from the gas. The oil which is not separated out will thus pass through the condenser with the gas to the evaporator and will accumulate there, particularlyl in the case of superheating machines in which only dry gas is drawn from the evaporator. This accumulation of oil in the evaporator causes a reduction in the etilciency of the evaporator by wetting the inner walls and thus reducing its heat conductivity and also'by decreasing the effective Working area ofthe evaporator. In addition there will be a reduction'in the quantity of oil available for lubricating and sealing the compressor and as a result the compressor will not function correctly. A y

The object of the present invention is to provide a return path to the compressor for oil passing with the refrigerating medium through the oil separator into the condenser.

According to this invention an oil collector in which the oil sinks to the bottom owing to its weightis provided, together with a dischargepipe for connecting the collector directly to the suction chamber of the compressorthe arrangement beings'uch that the discharge pipe of the oil collector is exposed to a lower pressure than the main discharge pipe of thel evaporator. Conveniently the diiierence in pressure between the pipes is obtained by connecting the evaporator to the compressor through a loaded valve preferably of the adjustable non-return type.4

When a multi-bladed rot/ary compressor with a crescent-shaped main suction chamber is provided, the discharge pipe of 'the oil collector maybe connected to a'subsidiary suetion chamber separated from the main suction chamber by at least one blade pitch. An additional evaporator may be arranged in the collectordischarge pipe preferably in such a way that liquid iow therethrough is in a downward direction.

The oil collector may be connected to the outlet side of the evaporator with or 4without a regulating valve in the collector discharge pipe, or may be arranged on the inlet side of and'below the evaporator.

The following is a description by way of example of several arrangements of refrigerating machine constructed in accordance with the invention with reference to the accompanying drawings, in which Figure l shows a sectional elevation of the rotary compressor, the other parts of the rerigerating machine being shown diagrammatically.

' Figure 2 is a sectional end elevation of th compressor on the line II-II of Figure l,

Figure 3 is a similar view to Figure l of a niodilied arrangement of refrigerating machine, and

` Figures 4 and 5 show diagrammatically -is in turn connected through a pipe 6 to an expansion valve 3. The expansion valve 3 is connected by a pipe 7 to an evaporator 4, the discharge pipe 8 of which is connected to the inlet side of the compressor 1. A closed circuit is thus formed through whichthe refrigerating medium circulates in',l the direction indicated by the arrows. YAn oil separator 9 is interposed in the pipe 5 so as to collect oil carried away by the refrigerating medium in the compressor and.. deliver it through a pipe 10 back to the compressor the direction of oil circulation being indicated by the dotted arrows. The rotary compressor itself, (Figures 1 and 2) Acomprises a working chamber 14 in which is mounted on a driving shaft 11 a multi-bladed rotor 12 having blades 13 which rotate in the direction indicated by the arrow. The working chamber 14 is bounded at the circumference by an eccentrically bored liner 16 and at the sides by two discs 17 in which are mounted ball .bearings 18 for supporting the shaft 11, an outer cover 15 being provided at each end of the casing.

Between the covers 15 and the discs 17 are oil pressure chambers 19" and 20 which are connected by the oil pipe 10 to the oil se arator 9 (Figure 1) and to each other by t e channels 21, 22 and 23. During the working of the compressor the oil circulates from the chambers 19 and 20 through the clearances between the various working parts of the compressor which it lubricates and seals into the working chamber 14, and from thence is carried as previously stated with the refrigerating medium into the oil separator from which, of course, it returns to the compressor by the pipe 10. The cover 15 through which the end of the shaft 11 passes is provided with a disc 24 pressed by a spring 25 against a machined face of the cover which thus forms a tight joint for closing the oil pressure chamber 20.

As it is impossible entirely to separate out all the oil from the refrigerating medium in the separator 9, lsome of this oil passes out from the separator through the pipe 5` to the condenser 2, pipe 6, throttling member 3, pipe 7, and through the evaporator 4. In order to prevent oil accumulating in the evapora-` tor an oil collectin chamber 26, hereinafter referred to as the o1l lcollector, is provided in the main discharge pipe 8 of the evaporator in which the oil sinks to the bottom on ac count of its weight. This oil collector is connected by a pipe 27, which is separate from the main discharge pipe 8 of the evaporator, to the suction chamber 28 ofthe compressor 1.

In order that the oil shall be withdrawn from the collector 26 to the compressor, it is necessary that the pipe 27 should be exposed to a pressure which is less than thatof the pipe 8. Accordingly, in the arrangement shown in Figure 1 a spring biased valve 29 1s provided .in the main discharge pipe of the evaporator. This valve 29 causes a fall in pressure between the suction chamber 28 and the pipe 8 and thus this pipe is exposed to a lower pressure than is the oil collector dis-- charge pipe 27. An additional evaporator 30 is included in the collector discharge pipe 27 together with a regulating valve 31 and a non-return valve 32.

Normallyoil passes through the pipe 27 and the evaporator 30, but when all the oily from the evaporator has passed into the compressor, refrigerating medium passes through the vaporatory 30 on the surface of` which ice therefore collects. This evaporator 30 therefore serves as an indication that there is no longer any oil in the evaporator and the regulating valve 31 can thus be closed or alternatively adjusted so as to regulate the flow of oil through the pipe 27 in accordance with the rate at which oil collects in the.

collector 26.

The valve 29 is ofthe non-return type in order that, in addition to producing a drop in pressure, it may also prevent the refrigerating medium or oil from returning to the the evaporator to which excess of refriger' ating liquid is supplied from the evaporator in addition to vapor. This excess which evaporates in the separator carries any oil which gets into the evaporator 4 into the oil collector or separator 26, where, owing to its weight, it sinks to the bottom and is thereupon drawn through the pipe 27 connected to the bottom of the separator into the compressor 1.

In the arrangement shown in Figure 3, the oil collector is inserted in the pipe 7 on the inlet side of and below the evaporator 4 so that oil carried by therefrigerating medium through the condenser and throttling member is deposited in the'collector 26 before passing into the evaporator. The oil is thus carried back to the compressor through the pipe 27 without passing through the evaporator 4.

In this arrangement the pipe 27 instead of being connected to the main suctionchamber 28 of the compressor, is connected to a subsidiary suction chamber 33 which is formed by reducing the vapor inlet opening 34 in the liner 16 so that there is at least one blade pitch between the end of the opening 34 and the inlet to pipe 27 The valve.29 can in this arrangement be arranged so that it does not produce a fall of pressure between the suction chamber of the compressor` and the pipe 8. X

, Thus, while in the arrangement shown in Figure 1 the diiierence of pressure between.

the pipes 8 and 27 is produced by the loadon the valve 29, that is to say, the s uction action on pipe 31 is determined and llmited while the volume drawn from the evaporator 30 is more independent in the arrangement shown in Figure 3`these conditions are reversed, that is the volume drawn'from thel additional evaporator 30 is limited whilst the .diiference of pressure between the two suction pipes 8 and 27 is not limited.

The compressor can therefore always draw from the additional evaporator as required by the condition and arrangement of the ma- V chine (e. g. the location of the main evaporator) although not more than a given total volume can be drawn into the compressor. The danger of liquid hammering `orlof wet working is thus less in the construction shown in Figure 3 than in that shown in Figure 1.

The suction pressure (always a little less than,l the pressure in the evaporator 4) will be such that sufiicient refrigerating mediumin liquid state, with any oil it may contain, will be drawn up to produce, when evaporated, the

correct volume for filling the blade spaces passing in front ofthe opening with gas at the correct pressure.

The additional evaporator through which the direction of flow is from the top to the bottom, in.order to ensure that theoil will pass through it and not remain therein as in the main evaporator, may be so dimensioned that vit is not nedessary to flood the evaporator down to the bottom in order to produce the necessary quantityof gas. .v Dry gas will therefore be drawn from the additional evaporator in spite of the fact that it is fed from the top.

' In the .arrangement shown in Figure 4 the main oil separator 9 is connected by anove'rflow pipe 35 directly to the pipe 6 leading from the condenser 2 to the throttling member 3.'

rIhrough this pipe 35 an excess of oil is constantly supplied to the collector 26 so that the oil level in the separator 9is maintained constant and the condenser 2 being by-rpassed the excess ofoil always keeps the oil level in the collector 26 at such a height above the inletopening ot the discharge pipe 27 of the collector that only pure oil and no refrigerating medium passes `from the collector 26 to thecompressor. In this way there is no likelihood of the compressor working wet and the constant supply of oil to the compressor through the pipe 27 i roves materially the lubrication of the working` parts and the reductionof leakage lossessi yFurthermore in this arrangement thecollector 26 may be ot a size such that it will hold a large quantity of oil so that in thev event ofany oillosses, as for example through the sealinor disc 24, the machine willnot be directly a ected by such leakage. As dur,

ing normal working no refrigerating medium passes through the pipe 27, an additional evaporator suchV as 30 (Figure 3) need not be provided in this pipe as no evaporation is likely to take place therein. If, however,

this pipe becomes coveredwith ice it will .serveas an indication that the machine is short of oil and therefore further oil must be added. In the arrangement shown in Figure 5, the

refrigerating medium passes through the' evaporator' 4@ in the downward direction so that the oil collector 26 arranged on the outlet side of the evaporator and belowit acts not only as an oil separator, but also as a liquid separator in which the excess of liquid refrigerating medium given 0E by the evaporator collects above the oil and is evaporated byabsorbing heat from its surroundings and is then drawn in with the other vapor charge pipe and connected if required on the outlet side of the second evaporator coil.

I claim:

1. In a\ refrigerating machine the combination of a compressor, an evaporator'an oil collector, apipe connecting the evaporator. to the oil collector, a refrigerant pipe connect-` ing the evaporator to the suction chamber of the compressor, a discharge pipe connectmg the oil collector to the compressor, and means for causing a lower pressure in the discharge pipe than the pressure in the refrlgerant pipe.

y i 2. In a refrigerating machine the combination of a'compressor, an evaporator, an ,oil collector, a the o1l collector, a refrigerant pipe connecting the evaporator to the suction chamber ont the compressor, a discharge pipe connecting the oil collector to the4 compressor, and

pipe connecting the evaporator to means for causing a diHerence between the pressure in the refrigerant sure in the discharge pipe.

n' 3. "In a refrigerating machine the combination of a compressor, an evaporator, an oil collector, a pipe connecting the evaporator to the oil collector, a refrigerant pipe connect-F pipe and the presthe compressor,

a dischar e i e connectin the oil collector g p p g to the compressor, means for f ing thev evaporator to the suction chamber of causing oil to How from the oil collector to the compressor, and a non-return valve in the discharge pipe for preventing a reverse flow of the oil.

4. In a refrigeratng machine the combination of a compressor, an evaporator, an oil collector, a pipe connecting the evaporator to the oil collector, a refrigerant pipe connecting the evaporator to the suction chamber of the compressor, a discharge pipe connecting the oil collector to the compressor, and a subsidiary evaporator inter,- posed within the discharge pipe.

5. In a refrigerating machine the combination of a compressor, an evaporator, an oil collector, a pipe connecting the evaporator to the oil collector, a refrigerant pipe connecting the evaporator to the suction chamber of the compressor, a discharge pipe connectingthe oil collector to the compressor, and a subsidiary evaporator interposed Within the discharge pipe, saidsubsidiary evaporator so arranged that the oil flow therein is in a downward direction. A

In testimony whereof I have aixed my si ature.

gn EMIL KGI. 

